<?php
// define array
$months = array(
  "jan" => "January",
  "feb" => "febuary",
  "mar" => null,
  "apr" => null
);

// search array for key
$a =  array_key_exists('jan', $months);var_dump($a);
$a =  isset($months['feb']);var_dump($a);
#######################################
$a =  array_key_exists('mar', $months);var_dump($a);
$a =  isset($months['apr']);var_dump($a);

